1. Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method each for applying a coating solution to a substrate such as a semiconductor wafer and the like and performing heat processing and subsequent cooling processing for the substrate.
2. Description of the Related Art
In a photolithography process of a semiconductor device, a semiconductor wafer is coated with a resist, a resist film formed by the coating is exposed in accordance with a predetermined circuit pattern, and the exposed pattern is developed, whereby a circuit pattern is formed on the resist film.
To perform such a series of processes, a resist coating and developing processing system has been conventionally used. The resist coating and developing processing system is so structured that a processing station in which various kinds of processing units for performing various kinds of processing for coating and developing on the semiconductor wafer are multi-tiered, a cassette station, in which cassettes for housing a plurality of semiconductor wafers are mounted, for carrying the semiconductor wafers into the processing station one by one and carrying a semiconductor wafer after processing out of the processing station and housing it in a cassette, an d a n interface section for receiving and passing the semiconductor wafer from/to an aligner, provided adjacent to the system, for exposing a resist film in a predetermined pattern, are integrally provided.
I n such a resist coating and developing processing system, for example, wafers are taken out of the cassette placed in the cassette station one by one and transferred to the processing station. After the wafer is first brought to a predetermined temperature in a cooling unit, a reflection prevention film (a bottom layer) is formed in a resist coating unit, and the wafer is subjected to heat processing in a hot plate unit (a heat processing unit) and cooled in a cooling unit (a cooling processing unit). Then, the wafer is coated with a photo resist film in a resist coating unit and subjected to baking processing in a heat processing unit.
Thereafter, the semiconductor wafer is transferred to the aligner from the processing station via the interface section, and the resist film is exposed in a predetermined pattern in the aligner. After the exposure, the semiconductor wafer is transferred again to the processing station via the interface section. First, the exposed semiconductor wafer is subjected to post-exposure bake processing in the hot plate unit, and coated with a developing solution in the developing unit after cooling, whereby the exposed pattern is developed. Thereafter, the wafer is subjected to postbake processing in the hot plate unit and cooled, thereby completing a series of processes. After the completion of the series of the processes, the semiconductor wafer is transferred to the cassette station and housed in a wafer cassette. Such processes are repeated successively for a predetermined number of semiconductor wafers one by one.
In such a series of resist coating and developing processing, as described above, heat processing is performed in the hot plate unit prior to the resist coating and the developing solution coating. However, since the resist coating and the developing solution coating are carried out in a temperature-adjusted atmosphere, the semiconductor wafer after the heat processing needs to be cooled in the cooling unit and controlled to a predetermined temperature.
By the way, in recent years, a demand for micromachining of a semiconductor device has been increased, and hence a high sensitive type resist solution is used. Accordingly, it is necessary to manage an atmosphere temperature in the resist coating with high accuracy.
Therefore, it is required to control a substrate temperature with high accuracy in the cooling unit before the substrate is carried into the resist coating unit. Further, temperature control with high accuracy is required also in the developing unit though the control is not so high in accuracy as that in the resist coating unit.
However, in the above-described resist coating and developing processing system, for the reason that semiconductor wafers are successively processed one by one at a high speed, many hot plate units and cooling units are mounted. Since the semiconductor wafers are transferred to the resist coating units from many cooling units, it is necessary to make these all cooling units temperature-controllable higher in accuracy than conventional ones in order to realize the temperature control with high accuracy in the cooling units, resulting in increased apparatus cost. On the other hand, if the number of the cooling units is reduced to avoid such an inconvenience, the cooling processing is delayed, which causes reduction in throughput.
An object of the invention is to provide a substrate processing apparatus and a substrate processing method capable of cooling a substrate with high accuracy and thereafter performing coating processing without increasing apparatus cost and decreasing throughput.
To solve the above problem, a first aspect of the present invention is a substrate processing apparatus for applying a coating solution to a substrate and performing heat processing and subsequent cooling processing for the substrate comprising: a coating processing unit for applying the coating solution to the substrate; a heat processing unit for performing the heat processing for the substrate; a plurality of first cooling processing units, which are temperature-controlled with comparatively low accuracy, for performing the cooling processing for the substrate; a second cooling processing unit, which is temperature-controlled with comparatively high accuracy, for performing the cooling processing for the substrate; and a transfer mechanism for transferring the substrate between the units, wherein the substrate which has been subjected to the heat processing by the heat processing unit is subjected to the cooling processing in the first cooling processing unit or the second cooling processing unit, and wherein when the substrate is transferred to the coating processing unit, the substrate is cooled in the second cooling processing unit at all times and then directly transferred to the coating processing unit.
Further, a second aspect of the present invention is a substrate processing method for applying a coating solution to a substrate and performing heat processing and subsequent cooling processing for the substrate, wherein cooling for the substrate after the heat processing is performed in a plurality of first cooling processing units, which are temperature-controlled with comparatively low accuracy, for performing the cooling processing for the substrate and in a second cooling processing unit, which is temperature-controlled with comparatively high accuracy, for performing the cooling processing for the substrate, and wherein when the substrate is transferred to the coating processing unit, the substrate is cooled in the second cooling processing unit at all times and then subjected to coating processing.
According to the present invention, the substrate which has been subjected to the heat processing is subjected to the cooling processing in the plurality of first cooling processing units which are temperature-controlled with comparatively low accuracy and in a second cooling processing unit which is temperature-controlled with comparatively high accuracy. When the substrate is transferred to the coating processing unit, the wafer is cooled at all times in the second cooling processing unit which is temperature-controlled with high accuracy and then transferred directly to the coating processing unit. Therefore, after rough cooling processing with low accuracy is performed in the plurality of first cooling processing units, the temperature control can be performed with high accuracy in a short period of time in the second cooling processing unit, thereby performing high accuracy cooling with no decrease in throughput. Moreover, it is sufficient to partly use such cooling processing units for performing temperature control with high accuracy, and thus an increase in apparatus cost can be suppressed.
In the aforesaid substrate processing apparatus, the substrate which has been subjected to the heat processing by the heat processing unit is subjected to the cooling processing in any of the first cooling processing units and thereafter to the cooling processing in the second cooling processing unit, whereby the substrate is temperature-adjusted in the cooling processing unit with the same high accuracy at all times and then transferred to the coating processing unit, resulting in a further increased accuracy in temperature control. Moreover, the rough cooling processing is performed in the first cooling processing unit and thereafter the cooling processing is performed in the second cooling processing unit, so that the cooling processing in the second cooling processing unit is performed sufficiently in a short period of time and many substrates can be successively cooled with high accuracy, resulting in improved throughput. More than that, a small number of high accuracy cooling processing units are sufficient, and thus there is little increase in apparatus cost.
It is preferable to further comprise control means for controlling the transfer mechanism so that when the substrate is transferred to the coating processing unit, the substrate is cooled in the second cooling processing unit at all times and then transferred directly to the coating processing unit.
Further, it is preferable that the second cooling processing unit is placed in an atmosphere of the coating processing unit. Thereby, the cooling processing in the second cooling processing unit can be performed in the same atmosphere as that of the coating processing unit, so that the accuracy of the cooling temperature can be further improved.
By way of typical examples of the coating processing units, given are a resist coating unit for applying a resist solution and a developing unit for applying a developing solution on a resist film to perform developing after the resist film on the substrate is exposed in a predetermined pattern.
The resist coating unit or the developing unit may have a control sensor for detecting a humidity of air supplied to the resist coating unit or the developing unit and a humidity control section for controlling the humidity based on a result detected by the control sensor. Thereby, it is possible to supply the air which is finely controlled in temperature and humidity to the resist coating unit and the developing unit.
The first cooing processing unit, which is temperature-controlled with low accuracy, may be cooled using a tap water. Thereby, the cooling processing unit can be fabricated at low cost.
Moreover, a cooling temperature of the first cooling processing unit which is temperature-controlled with low accuracy may be controlled at a temperature lower than a cooling temperature of the second cooling processing unit which is temperature-controlled with high accuracy, thereby reducing the period of cooling time of the substrate.
The cooling temperature of the first cooling processing unit which is temperature-controlled with low accuracy is set lower than a desired substrate adjustment temperature to be controlled, thereby further reducing the period of cooling time of the substrate. The cooling may be performed so that the high accuracy cooling temperature before the substrate is transferred to the resist coating unit is controlled with accuracy higher than that of the high accuracy cooling temperature before the substrate is transferred to the developing unit, thereby obtaining the resist coating unit and the developing unit at low cost.
These objects and still other objects and advantages of the present invention will become apparent upon reading the following specification when taken in conjunction with the accompanying drawings.